This invention relates to a gripper device for thin, plate-like parts, especially sheet-metal parts, with a plurality of suction cups disposed on the underside of a carrier frame.
Gripper devices with suction cups are frequently used in industry to separate and/or change the position of thin, plate-like parts such as e.g. sheet-metal parts. They are particularly suitable for use in combination with robots when the aim is to achieve a largely automated method of working.
Where gripper devices of the said type are not intended to be used exclusively with one and the same plate-like part, the positions of the suction cups have to be adjustable to a certain degree. For this purpose the suction cups may be disposed on star or cross-shaped carrier frames with arms that can be adjusted, and, in particular, can be extended and retracted radially. It is necessary in particular to be able to make adjustments in order to take account of the bending characteristics of very thin plates, or to position the suction cups against the flat surfaces of three-dimensional parts.
Until now, the adjustment process has been mainly carried out by hand. When parts have to be changed frequently, however, this procedure is no longer feasible for economical reasons. To date, largely automatable solutions have comprised positioning motors with relatively precise position transducers and appropriate gears for adjusting the suction caps. These solutions were relatively complex and costly. They also tended to increase the weight of the carrier frame and were therefore also associated with disadvantages from the energy consumption point of view.
The invention is based on the task of equipping a gripper device of the above type, i.e. one which is used in conjunction with a robot, with a simple, cost-effective means of adjusting the suction cups.
According to the invention, this task is solved by a gripper device of the above type which is characterized in that the suction cups are fixed to the outer ends of four gear racks which are disposed as a cross and can be displaced longitudinally along two superimposed planes, in that in the centre of the cross formed by the racks, mounted in a vertical axis, there is a toothed gear which extends over both superimposed planes, in that the gear racks engage with the toothed gear in pairs from diametrically opposed sides, and in that a control rod with a gear rack profile engages with the toothed gear on a third plane, said control rod having an engaging device at one radially external end.
In a mechanism of this type, the gear racks are adjusted radially in that the engaging member is made to engage with a fixed point in the vicinity of the gripper device, and the gripper device is then moved horizontally by the associated robot in such a way that the control rod is displaced radially towards the exterior or the interior. When the control rod is displaced longitudinally the toothed gear rotates, and the rotation of the toothed gear extends or retracts the four gear racks.
The gear racks are preferably positioned between top and bottom clamping plates, between which they are displaced within longitudinal guides. Once the correct adjustment has been found for the gear racks, they can be clamped in position by clamping the clamping plates together. Air cylinders are provided for this purpose on top of the top clamping plate or underneath the bottom clamping plate, whose piston rods run through the corresponding clamping plate and are connected with the opposite clamping plate.